The fathers who received oxytocin showed higher levels of activity in the regions of the brain linked with reward, empathy and attention.

We gave fathers a boost of oxytocin, a hormone known to be involved in maternal caregiving and mother-offspring bonding, via a nasal spray. We then measured their brain activity when they looked at pictures of their 1- or 2- year old sons or daughters. The fathers who received oxytocin showed higher levels of activity in the regions of the brain linked with reward, empathy and attention than fathers who had received a placebo (a nasal spray with no oxytocin in it).

Oxytocin is higher on average in fathers compared with men who are not fathers. Oxytocin levels increase in men over the first six months of fatherhood. Other research has shown that oxytocin promotes physical stimulation, play and emotional synchrony with infants among human fathers.

Other hormones also change in involved fathers . For example, testosterone decreases and this is also associated with fathers becoming more caring for their infants.

We measured brain activity with functional MRI and presented fathers with a range of stimuli – a photo of an unknown child of a similar age, a photo of an unknown adult and a recording of an infant’s cry (but not their own infant). Oxytocin only changed the response to pictures of their own child. A parallel experiment did the same with another hormone, vasopressin, but this hormone had no effect in this context.